Looking for some educated guesses on this!
See here for the engine rebuild: http://grassrootsmotorsports.com/forum/build-projects-and-project-cars/rebuilding-the-cannon-first-atv-motor-rebuild/62693/page1/
So, my engine made it about a year before failing, and I'd like to not blame it on my lack of engine building skills but its hard to tell. I think a combination of running a bit lean despite a rich tune (FPR?), an intermittent cooling fan, and flaw in the engine case but thats just to help me sleep at night 
Pics of the outside:
So the sleeve was fine, but the piston skirt is unhappy:
Inside the case view; second pic looking from exhaust end forward you can kinda see the casting flaw area:
And a shot of the head, for fun:
So, any opinions on what may have caused/contributed to this? And most importantly, saveable with some JB weld? 
I'm going to swap parts over into another engine that didn't run that I picked up for cheapish, but was considering swapping all of the other internals into this welded case and then running it for as long as it'll go, and spend minimal money on getting it running.
TLDR: Cracked engine case, what caused it and what would it take to get the cracked case fixed, on the cheap or the right way?
pav5069
New Reader
1/16/15 8:09 p.m.
What kind of motor is it? Is it a 450? I know a lot of ppl JB welding the cases and had some good results.
In reply to pav5069:
Its a 440 (actually a 432cc) out of a 2002 Cannondale Speed.
PS - don't buy a quad from a company that went out of business shortly after introducing a new ATV/Motorcycle design and a new engine design 
Is that part of the water jacket, or solid? I'd stop drill it and have it welded either way, if it propagates you'll eventually blow the top end off the block.
In reply to Kenny_McCormic:
It's solid, and below the waterline. It's sorta right in the middle of the piston stroke, if the sleeve were there.
On the internal pics, the ledge about 3/4" above the crack is where the piston sleeve seals the crankcase from the water jacket.
Just to clarify, it's below where the head bolts go into the block, right? If it were above I would be less concerned.
In reply to Kenny_McCormic:
Ah, gotcha. Yea, at the closest point to the head bolts it's about 3/4" below where I'm guessing the stud threads stop (first pic)
Yeah, weld it. That's a load bearing area, in tension. I suppose you could rig it up farm fix style by stop drilling it and covering it with a steel plate and plenty of machine screws, all sealed up with generous amounts of JB weld, but welding it would be best.
1) I'd weld it, JB Weld is not real good for these type situations and 2) ATK Motorcycles bought what remained of Cannondale's motorcycle and ATV program, they now sell parts etc. http://www.atkusa.com/atk/(S(v0udox55ew5neg45xyqyur45))/default.aspx
Dean Rule of JB weld Versus Real welding
JB weld if the item being welded is pointed away from important body parts.
TIG/MIG weld if there is any chance that when it does come apart you will be damaged.
